Writing instrument



FIG. 1 is a front elevational view of a writing instrument showing my new design, the rear view being a mirror image thereof;

FIG. 2 is a right side elevational view;

FIG. 3 is a left side elevational view;

FIG. 4 is a top plan view; and,

FIG. 5 is a bottom plan view thereof.

The portions of the writing instrument depicted by means of broken lines have been shown for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a writing instrument, as shown and described. 